The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Conventional vehicular fuel systems, such as those installed in vehicles, such as automobiles, may employ a “return fuel system” whereby a fuel supply tube is utilized to supply fuel to an engine and a fuel return line is utilized to return, hence “return fuel system,” unused fuel to a fuel tank. Such return fuel systems require the use of both a supply line to and a return fuel line from the engine. More modern vehicles typically employ a “returnless fuel system” that may either be mechanically or electronically controlled.
Regarding such returnless fuel systems, such as a mechanical returnless fuel system (“MRFS”), only a fuel supply line from a fuel tank to the engine is utilized; therefore, no return fuel line from the engine to the fuel tank is necessary. As a result, an MRFS delivers the volume of fuel required by an engine, regardless of the varying degree of the volume of fuel required; however, the fuel pump operates at 100% capacity irrespective of engine demand, with excess fuel being discharged through a fuel pump module via the pressure regulator. In a MRFS, interaction with an electronic control module or vehicle body control module may not normally occur.
During operation of a vehicle employing an MRFS such as that discussed above, the engine typically cycles through periods of acceleration, intermediate speed operation, deceleration, idle and engine off conditions. The MRFS pumps fuel to the rail to maintain a constant pressure based on the pressure regulator. However, the rail pressure may increase or decrease due to the various cycles.
An additional problem may occur upon engine start-up when the vehicle is exposed to high ambient temperatures after engine shutoff. In such a circumstance, residual engine heat, along with the ambient heat, may cause fuel pressure within the fuel rail to vaporize thereby compromising engine restart.